1. Centre for Ecology and Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxon OX10 8BB, UK
2. Institute of Environmental Studies, DEMETRA, Via Olona 7, I-00198 Rome, Italy
3. Department of Applied and Environmental Biology, The Rivers State University of Science and Technology, Port Harcourt, Rivers State, Nigeria
4. Centre d'études biologiques de Chizé, CNRS, Villiers en Bois 79360, France
5. CNR, Institute of Ecosystem Studies, via Borelli 50, I-00161 Rome, Italy
6. Piazza Capri 20, I-00141 Rome, Italy
7. Department of Environment and Conservation, PO Box 51, Wanneroo, Western Australia 6946, Australia